Both forms are correct. Flavour and flavor are two correct spellings of the same word. The difference is that the first one is the British English version and the second one is the American English version. Besides spelling, there is no difference in meaning. However, there is a minor distinctiveness in pronunciation, Britons usually use the form /ˈfleɪ.vər/, and Americans pronounce it as /ˈfleɪ.vɚ/. There are many words that in British English have ending -our and their American equivalents end with -or.

Correct spelling, explanation: variant used in British English.

Correct spelling, explanation: spelling popular in American English.

Definition of flavor/flavour:
Noun: the way something taste, e.g. food, drinks, etc.;
I love the flavour and smell of freshly brewed coffee in the morning.
I hate the flavor of Brussel sprouts since I was a child.
Verb: to give a particular taste to something;
I like to flavour anything with a lot of pepper.
My mum never flavors anything enough.